Bowie's daughter Brenda issued a heart-wrenching call for information about her missing mother who disappeared 36 years ago.

"I was only six-years-old when my mother disappeared and it has been hard living my life not knowing what happened to her," Brenda told the media on Friday.

"Also, my brother Warren passed away in 2016. He also died without knowing what happened to our mother. If this ... brings anyone forward ... my hope is to lay them to rest together."

The NSW government announced a $1 million reward on Friday for information that could help solve the cold case of Roxlyn Bowie, a NSW mother who disappeared without a trace.

Bowie, 31, was last seen at her Walgett home in Northern NSW at about 6pm on June 5, 1982.

She left behind her children Brenda then six and Warren, then nearly two. They were lying alone in their beds when she vanished.

"From what I remember of my mum, it just seems impossible that she would have left my brother or I and I just ask that if any of the public can put themselves in my position. I just want answers," Brenda said on Friday.

Roxlyn and her husband John. Image: Supplied.

The massive million-dollar sum aims to encourage anyone with information to come forward.

"This is a substantial amount of money and a significant reward and the reason it is a significant reward announced by the government is because we want justice to be done," Detective Superintendent Daniel Doherty said on Friday.

"We believe there are people out there who know exactly what happened to Roxlyn … and we hope that this reward will be the catalyst for them to come forward."

In October this year, Police renewed their appeal for assistance over Bowie's disappearance and suspected murder.

"Roxlyn Bowie was described as a shy and quiet woman, and a beloved daughter and mother," said Doherty in October 2018.

"From all accounts, Mrs Bowie was utterly devoted to her two young children, which makes her disappearance very puzzling to those who knew her well."